1. Field of the Invention
This invention relates to the control of a manually operated gear shifting mechanism and more particularly to such a control for regulating the movement of the gear selection shaft.
2. Description of the Prior Art
Front wheel drive motor vehicles of the transaxle type, wherein the engine and the transmission are positioned transversely with respect to the fore and aft axis of the motor vehicle, are known to cause uncertainty as to the actual speed ratio in which the transmission is operating. The vehicle operator has a less certain feedback from the transmission performance in relation to the position of the shift handle than with conventional longitudinal engine-transmission arrangements. Transaxle motor vehicle design requires that the transmission be located at a much more forward position in the vehicle than if the vehicle were of the in-line type. Conventional motor vehicles have the manual transmission positioned immediately below the gear selection shaft whose position is controlled by the vehicle operator. The response of the transmission to the control of the operator occurs over a relatively shorter path and therefore the operator has a more positive indication of the actual speed ratio in which the transmission is operating. Because of the greater structural stiffness of the connecting mechanism over shorter distance between the gear selector shaft and the transmission, the vehicle operator is given continual and accurate feedback of the relationship between the position of the selector shaft and the performance of the transmission.
On the other hand, manual transaxle vehicle design requires a distance of about three to four feet between the location of the selector shaft handle and the transmission that it controls. Because of the resultant structural deformation of the various load carrying members of the shifting mechanism and the tolerances associated with the numerous mechanical joints of the mechanism, the vehicle operator has a vague and uncertain indication of the speed ratio in which the transmission is operating. In addition to the greater length over which selector input must be transmitted in a transaxle vehicle, vehicles of this type are susceptible of fore and aft rotation of the engine and transmission assembly about the transverse vehicle axis. Rotation of this sort occurs because of variations which are continually occurring in normal vehicle operations. Movement of the assembly with respect to the vehicle chassis contributes to the vague and ambiguous indication given the vehicle operator of the relationship between the actual speed ratio in which the transmission is operating and the position of the shift handle whose position he controls.
A further contribution to the uncertainty associated with shift handle operation is the requirement in transaxle vehicles that fore and aft motion of the shift handle actually produce right-left motion of the shaft that transmits operator control input to the gear selector mechanism. Furthermore, right-left movement of the selector handle must cause the gear selector shaft to experience a rotary movement about its longitudinal axis in transaxle vehicles to maintain the conventional shifting pattern of the operator-controlled shift handle.
Conventional in-line engine transmission arrangements therefore have generally produced a positive and certain signal to the vehicle operator of the effect of the movement he produces on the shift handle and its relationship to the transmission performance. Transaxle vehicles on the other hand are encumbered by a vagueness in the feedback given the vehicle operator as a result of the control he exercises over the gear selector shaft.